Historically wafer writing in lithography and scanning in metrology and inspection systems have used linear stepping or scanning motion to translate a substrate. Rectilinear motion has the advantages of simplicity in the rendering process, since the die on a semiconductor wafer are typically arranged in the direction of motion. In Cartesian (XY) reticle writing the data path follows the prevailing directionality in the geometry to be rendered. However, the factor limiting the throughput is the mechanical motion of the Cartesian stage. As the data path electronics get faster, this mechanical limitation of Cartesian systems becomes more limiting, and the data path rendering in polar coordinates becomes easier. The data path rendering speed is expected to continue to follow the Moore's law and improve with newer generations of semiconductors, while throughput of Cartesian stages is subject to relatively slow progress in precision engineering.
Reciprocating stages have a practical limit of turnaround time at the end of the swath of about 100 milliseconds. To shorten this time mechanics must allow higher bandwidths. The use of high performance materials allows only for moderate improvements of highest scanning speed. The increases in acceleration at the end of the motion also have their limitation in power of actuators, heat dissipation, reaction on the vibration isolation system and the machine base, settling after acceleration etc.
It is within this context that embodiments of the present invention arise.